Planar antenna apparatus

Abstract

An antenna apparatus including a dielectric substrate, a planar antenna element disposed on the substrate, and a waveguide for propagating electromagnetic waves to or from the planar antenna element. The waveguide includes at least a first conductor and a second conductor extending along each other. Near a connection portion formed between the first and second conductors and the planar antenna element, there is provided a taper region in which a distance between mutually-facing edge portions of the first conductor and the second conductor increases approximately monotonically toward the planar antenna element.

1. An antenna apparatus comprising:
 a dielectric substrate; 
 a planar antenna element disposed on the substrate; and 
 a waveguide for propagating electromagnetic waves to or from the planar antenna element, 
 wherein the waveguide comprises at least a first conductor and a second conductor extending along each other, and near a connection portion formed between the first and second conductors and the planar antenna element, there is provided a taper region in which a distance between mutually-facing edge portions of the first conductor and the second conductor increases approximately monotonically toward the planar antenna element. 
 
   
   
     2. An antenna apparatus according to  claim 1 , wherein the first conductor comprises a conductor comprises a center conductor, and the second conductor comprises at least a grounded conductor. 
   
   
     3. An antenna apparatus according to  claim 2 , wherein the waveguide is disposed in the same plane as the planar antenna element, and comprises a co-planar waveguide having a center conductor of the first conductor connected to the planar antenna element, and grounded conductors of the second conductor, each of which is formed at a distance from the center conductor on each side of the center conductor. 
   
   
     4. An antenna apparatus according to  claim 1 , wherein the planar antenna element is a bow-tie antenna element having an isosceles triangular shape with a vertical angle of a desired value. 
   
   
     5. An antenna apparatus according to  claim 1 , wherein the planar antenna element is a teardrop-shaped antenna element whose shape is composed of a portion of an isosceles triangular shape with a vertical angle of a desired value and an arc of a circle inscribed in the isosceles triangle. 
   
   
     6. An antenna apparatus according to  claim 1 , wherein the planar antenna element is comprised of teardrop-shaped structures, each composed of a portion of an isosceles triangular shape with a vertical angle of a desired value and an arc of a circle inscribed in the isosceles triangle, arranged with their apexes facing each other. 
   
   
     7. An antenna apparatus according to  claim 6 , wherein the waveguide is an unbalanced line which is converted into a balanced line via the taper region, and connected to the planar antenna element. 
   
   
     8. An antenna apparatus comprising:
 a dielectric substrate; and 
 a planar antenna element disposed on the substrate, 
 wherein the planar antenna element comprises teardrop-shaped structures, each composed of a portion of an isosceles triangular shape with a vertical angle of a desired value and an arc of a circle inscribed in the isosceles triangle, arranged with their apexes facing each other.